I mostly play DOSBox stuff. Other notable stuff, Doom, Quake (2) and Hexen II have some native ports, and I do some stuff via WINE such as the Disciples series and I forget what else. Some (S)NES/Genesis emulation too.

Most native games for Linux are kind of shit in my experience though, aside from Wesnoth and Dungeon Crawl.

Pro tip: ditch GNOME in favor or a light window manager like IceWM, as it's a bloated shitpig-express. Doing this switch can make a big performance difference for some stuff (DOSBox in particular.)